Cooling fan and heat dissipation device having the same

ABSTRACT

A heat dissipation device includes a heat sink and a cooling fan. The heat sink includes a substrate and a plurality of fins. The cooling fan includes a fan housing defining an air inlet and an air outlet at two opposite sides thereof, and an impeller received in the fan housing and mounted to a supporting base provided at the air inlet. The air outlet is positioned adjacent to the heat sink. The impeller includes a hub, a plurality of main blades and auxiliary blades. The hub includes a top wall located at the air outlet and a sidewall extending from the top wall. The main blades extend radially and outwardly from the sidewall. The auxiliary blades located on the top wall extend from a center of the top wall towards an outer periphery of the top wall.

BACKGROUND

1. Technical Field

The present disclosure relates to heat dissipation, and particularly to a heat dissipation device having an improved cooling fan.

2. Description of Related Art

With continuing development of electronic technology, heat-generating electric components such as CPU (central processing unit) is generating more and more heat which requires immediate dissipation. Generally, a heat dissipation device provides such heat dissipation. The heat dissipation device includes a heat sink thermally attached to the CPU to absorb heat therefrom and a cooling fan mounted on the heat sink for facilitating removal of heat from the heat sink.

The cooling fan includes a housing and an impeller received in the housing. The housing defines an air inlet at one side and an air outlet at an opposite side along an axial direction thereof. The impeller includes a hub and a plurality of blades extending radially and outwardly from the hub. The hub includes a flat top wall and a cylindrical sidewall extending downwardly from an outer periphery of the top wall. The blades extend radially from the sidewall of the hub. When assembled, the impeller is received in the housing with the top wall of the hub located at the air inlet. When the cooling fan operates, the top wall prevents air from flowing into an area just under the top wall, so that the area just under the top wall lacks airflow and forms as an airflow dead area to cause heat to accumulate there. Thus, the efficiency of the cooling fan is affected accordingly.

Therefore, a heat dissipation device having an improved cooling fan is desired to overcome the above describe shortcomings.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the embodiments can be better understood with references to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present heat dissipation device. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.

FIG. 1 is an assembled, isometric view of a heat dissipation device in accordance with a first embodiment.

FIG. 2 is an exploded, isometric view of the heat dissipation device of FIG. 1.

FIG. 3 is an isometric view of an impeller of the heat dissipation device of FIG. 1.

FIG. 4 is an isometric view of an impeller in accordance with a second embodiment.

FIG. 5 is a cross-sectional view of the impeller of FIG. 4, taken along a line V-V thereof.

FIG. 6 is an isometric view of an impeller in accordance with a third embodiment.

FIG. 7 is a cross-sectional view of the impeller of FIG. 6, taken along a line VII-VII thereof.

FIG. 8 is an isometric view of an impeller in accordance with a fourth embodiment.

FIG. 9 is an isometric view of an impeller in accordance with a fifth embodiment.

FIG. 10 is an isometric view of an impeller in accordance with a sixth embodiment.

DETAILED DESCRIPTION

Referring to FIGS. 1 and 2, a heat dissipation device according to a first embodiment is shown. The heat dissipation device is mounted on an electronic component, such as a CPU (not shown), for dissipating heat therefrom. The heat dissipation device includes a heat sink 10, a cooling fan 20 and a fixing member 19 mounting the cooling fan 20 to the heat sink 10. The heat sink 10 includes a substrate 12 mounted on the electronic component, a plurality of fins 14 located on the substrate 12 and a pair of heat pipes 16 thermally connecting the substrate 12 with the fins 14. The fins 14 are parallel to and spaced from each other. Each heat pipe 16 is U-shaped, and includes an evaporator section embedded in the substrate 12 and a condenser section extending through the fins 14.

The cooling fan 20 includes a hollow, cylindrical fan housing 22 and an impeller 24 received in the fan housing 22. An air inlet 17 is defined at a top side of the fan housing 22. An air outlet 18 opposite to the air inlet 17 is defined at a bottom side of the fan housing 22. A supporting base 21 is formed on a central portion of the fan housing 22 at the air inlet 17 for mounting the impeller 24 thereon. When the cooling fan 20 and the heat sink 10 are assembled, the air outlet 18 faces the heat sink 10 with the impeller 24 invertedly mounted between the air outlet 18 and the air inlet 17 of the fan housing 22. The air outlet 18 is located between the heat sink 10 and the air inlet 17. In other words, the air outlet 18 is located nearer to the heat sink 10 in comparison to the air inlet 17.

Referring to FIG. 3, the impeller 24 includes a hub 23, a plurality of main blades 25 and a plurality of auxiliary blades 26. The hub 23 includes a circular top wall 232 and a cylindrical sidewall 234 extending downwardly from an outer periphery of the top wall 232. The top wall 232 is flat and located at the air outlet 18 of the cooling fan 20. The auxiliary blades 26 are located on a top surface of the top wall 232 and between the top wall 232 of the hub 23 and the heat sink 10. The main blades 25 extend radially and outwardly from an outer circumferential surface of the sidewall 234.

Each auxiliary blade 26 extends upwardly and perpendicularly from the top surface of the top wall 232 and radially and curvedly from a center of the top wall 232 towards the outer periphery of the top wall 232. Each auxiliary blade 26 includes an inner first end 260 connected to the center of the top wall 232 and an outer second end 261 extending to the outer periphery of the top wall 232. The second ends 261 of the auxiliary blades 26 are evenly arranged along a circumferential direction of the top wall 232, while the first ends 260 of the auxiliary blades 26 are converged at the center of the top wall 232. Each auxiliary blade 26 has a constant height from the first end 260 to the second end 261. Each auxiliary blade 26 has an upper edge 262 on a top side thereof that is away from the top surface of the top wall 232. The upper edges 262 of the auxiliary blades 26 are coplanar.

During operation, the substrate 12 of the heat sink 100 absorbs heat from the electronic component and transfers it to the evaporator section of the heat pipe 16, and then to the condenser section of the heat pipe 16. The condenser section of the heat pipe 16 transfers the heat to the fins 14 which dissipate the heat to a space between each two neighboring fins 14 such that the air in the space is heated. The impeller 24 of the cooling fan 20 rotates and the main blades 25 drive outside cool air into an area between the housing 22 and the sidewall 234 of the hub 23 via the air inlet 17, and then the cool air is blown downwardly towards the fins 14 via the air outlet 18 to take the heated air in the space between the fins 14 away from the heat sink 10. At the same time, the auxiliary blades 26 on the top wall 232 of the hub 23 rotate with the impeller 24 to agitate the air just under the top wall 232 of the hub 23, wherein the air is guided from the center of the top wall 232 to the outer periphery of the top wall 232 by the auxiliary blades 26, and then the air is blown towards the fins 14 by the main blades 25. Thus, the airflow dead area existed originally under the hub 23 is eliminated in the present embodiment due to the presence of the auxiliary blades 26 on the top wall 232 of the hub 23.

FIGS. 4 and 5 show an impeller 44 in accordance with a second embodiment of the disclosure, differing from the previous impeller 24 only in that a hub 43 of the impeller 44 includes a dome-shaped top wall 432, and a plurality of auxiliary blades 46 formed on the top wall 432, wherein each auxiliary blade 46 has a varied height. The top wall 432 is tapered from an outer periphery of the top wall 432 towards a center of the top wall 432 and forms a conical tip at the center, such that the top surface of the top wall 432 is declined from the outer periphery towards the center of the top wall 432 when the impeller 44 is invertedly mounted on the supporting base 21 of the fan 20 of FIG. 1. The auxiliary blades 46 are able to guide the air just under the top wall 432 to flow smoothly from the center towards the outer periphery of the top wall 432. Thus, the airflow dead area just under the top wall 432 of the hub 43 is eliminated. All of the upper edges 462 of the auxiliary blades 46 are coplanar, such that the height of each auxiliary blade 46 gradually and smoothly increases from the center of the top wall 432 towards the outer periphery of the top wall 432.

Referring to FIG. 6 and FIG. 7, an impeller 54 in accordance with a third embodiment is shown. The impeller 54 has a configuration similar to the second impeller 44 only differing in that each main blade 55 has an upper edge 550 higher than the top wall 432 of the hub 43. The upper edges 550 of the main blades 55 are coplanar to the conical tip of the top wall 432. As the upper edge 550 of each main blade 55 is higher than the top wall 432 of the hub 43, the main blades 55 have a larger size than the main blades 25 of the impeller 44 of FIG. 4.

FIG. 8 shows an impeller 64 in accordance with a fourth embodiment of the present disclosure, differing from the impeller 24 of the previous first embodiment only in that the auxiliary blades 66 extend radially and linearly from the center of the top wall 232 towards the outer periphery of the top wall 232.

FIG. 9 shows an impeller 74 in accordance with a fifth embodiment. The impeller 74 is similar to the impeller 24 of the previous first embodiment, differing in that each of the auxiliary blades 76 has an inner section 760 with a varied height and an outer section 761 with a constant height. A top edge of the inner section 760 of each auxiliary blade 76 extends upwardly from the center of the top wall 232 towards the outer section 761. A top edge of the outer section 761 of each auxiliary blade 76 extends horizontally from the inner section 760 towards the outer periphery of the top wall 232. The top edge of the inner section 760 is lower than the top edge of the outer section 761, such that a concave 763 is formed at the center of the top wall 232.

Referring to FIG. 10, an impeller 84 according to a sixth embodiment is shown. The impeller 84 has a configuration similar to the impeller 24 of the previous first embodiment, but differing in that each of the auxiliary blades 86 has an inner first end 860 adjacent to the center of the top wall 232 and an outer second end 861 at the outer periphery of the top wall 232. The first ends 860 of the auxiliary blades 86 are spaced from the center of the top wall 232 of the hub 23 and arranged on a circumference of an imaginary circle around the center of the top wall 232. The imaginary circle is concentric with the outer periphery of the top wall 232.

It is to be understood, however, that even though numerous characteristics and advantages of the disclosure have been set forth in the foregoing description, together with details of the structure and function of the embodiments, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed. 

1. A cooling fan, comprising: a fan housing defining an air inlet and an air outlet at two opposite sides along an axial direction of the fan housing, respectively; an impeller being received in the fan housing and mounted to a supporting base provided at the air inlet, the impeller comprising: a hub including a top wall being located at the air outlet and a sidewall extending downwardly from the top wall; a plurality of main blades extending radially and outwardly from the sidewall; and a plurality of auxiliary blades being located on the top wall extending from a center of the top wall to an outer periphery of the top wall.
 2. The cooling fan of claim 1, wherein the auxiliary blades extend upwardly and perpendicularly from the top wall of the hub.
 3. The cooling fan of claim 1, wherein the auxiliary blades extend radially and curvedly from the center of the top wall towards the outer periphery of the top wall.
 4. The cooling fan of claim 1, wherein the auxiliary blades extend radially and linearly from the center of the top wall towards the outer periphery of the top wall.
 5. The cooling fan of claim 1, wherein each auxiliary blade has an inner first end connected to the center of the top wall and an outer second end extending to the outer periphery of the top wall, and the first ends of the auxiliary blades are converged at the center of the top wall.
 6. The cooling fan of claim 1, wherein each auxiliary blade has an inner section with a varied height and an outer section with a constant height, and the height of the inner section is lower than that of the outer section, such that a concave is defined at the center of the top wall.
 7. The cooling fan of claim 1, wherein each of the auxiliary blades has an inner first end adjacent to the center of the top wall and an outer second end extending to the outer periphery of the top wall, and the first ends of the auxiliary blades are spaced from the center of the top wall of the hub and arranged on a circumference of an imaginary circle which is concentric with the outer periphery of the top wall.
 8. The cooling fan of claim 1, wherein the top wall of the hub is doom-shaped, and tapered from the outer periphery of the top wall towards the center of the top wall and forms a conical tip at the center of the top wall.
 9. The cooling fan of claim 8, wherein each auxiliary blade has an upper edge and the upper edges of the auxiliary blades are coplanar, such that a height of each auxiliary blade gradually increases from the center of the top wall towards the outer periphery of the top wall.
 10. The cooling fan of claim 1, wherein each main blade has an upper edge higher than the top wall of the hub.
 11. A heat dissipation device, comprising: a heat sink comprising a substrate and a plurality of fins being located on the substrate; a cooling fan being attached to the heat sink, comprising: a fan housing defining an air inlet and an air outlet at two opposite sides along an axial direction of the fan housing, respectively, the air outlet being located adjacent to the heat sink and the air inlet being located distant from the heat sink; an impeller being received in the fan housing and mounted to a supporting base provided at the air inlet, the impeller comprising: a hub including a top wall being located at the air outlet and a sidewall extending downwardly from the top wall towards the air inlet; a plurality of main blades extending radially and outwardly from the sidewall; and a plurality of auxiliary blades being located on the top wall extending from a center of the top wall to an outer periphery of the top wall.
 12. The heat dissipation device of claim 11, wherein the auxiliary blades extend upwardly and perpendicularly from the top wall of the hub.
 13. The heat dissipation device of claim 11, wherein the auxiliary blades extend radially and curvedly from the center of the top wall towards the outer periphery of the top wall.
 14. The heat dissipation device of claim 11, wherein the auxiliary blades extend radially and linearly from the center of the top wall towards the outer periphery of the top wall.
 15. The heat dissipation device of claim 11, wherein each auxiliary blade has an inner first end connected to the center of the top wall and an outer second end extending to the outer periphery of the top wall, and the first ends of the auxiliary blades are converged at the center of the top wall.
 16. The heat dissipation device of claim 15, wherein each auxiliary blade has an inner section with a varied height and an outer section with a constant height, and the height of the inner section is lower than that of the outer section, such that a concave is defined at the center of the top wall.
 17. The heat dissipation device of claim 11, wherein each of the auxiliary blades has an inner first end adjacent to the center of the top wall and an outer second end extending to the outer periphery of the top wall, and the first ends of the auxiliary blades are spaced from the center of the top wall of the hub and arranged on a circumference of an imaginary circle which is concentric with the outer periphery of the top wall.
 18. The heat dissipation device of claim 11, wherein the top wall of the hub is doom-shaped, and tapered from the outer periphery of the top wall towards the center of the top wall and forms a conical tip at the center of the top wall.
 19. The heat dissipation device of claim 18, wherein each auxiliary blade has an upper edge and the upper edges of the auxiliary blades are coplanar, such that a height of each auxiliary blade gradually increases from the center of the top wall towards the outer periphery of the top wall.
 20. The heat dissipation device of claim 11, wherein each main blade has an upper edge higher than the top wall of the hub. 